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激光熔覆WC-Ni基超硬梯度复合涂层的组织与性能 总被引:3,自引:1,他引:2
利用激光宽带熔覆技术在45钢表面制备了WC-Ni基超硬梯度复合涂层.对激光熔覆层用SEM、EDS、XRD进行观察和分析.对比研究了单一熔覆层、梯度熔覆层的熔覆层形貌、缺陷状态、硬度及其分布.结果表明,单一熔覆层易出现宏观裂纹、界面处熔合差等缺陷;梯度激光熔覆层逐级过渡的结合形式缓解了应力集中,使应力合理分布.在优化的工艺参数下,通过连续控制微观结构要素,可以实现成分、组织的梯度变化,获得无气孔、无裂纹的梯度熔覆涂层.其中,梯度熔覆层组织主要是由γ-Ni、WC等相组成,涂层的硬度值从熔覆层至基体呈梯度降低趋势,外层平均硬度可达2000 HV0.1以上. 相似文献
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《中国有色金属学会会刊》2017,(3)
为提高碳钢的耐腐蚀性能,利用高功率连续半导体激光器分别以6和12 mm/s的熔覆速度,在E235低碳钢基体上成功制备了哈氏合金涂层。利用稀硝酸溶液溶去E235钢基体后,获得激光熔覆层与钢基体之间的界面,并对该界面的显微组织、化学组分以及力学性能进行系统研究。研究发现在涂层/基体界面上的晶界处,存在着一种特殊"边缘",而这种特殊"边缘"由真实晶界与发生晶界腐蚀后留下的腐蚀痕迹所组成。界面主要呈现出由激光熔覆后迅速冷却和Ni元素向界面扩散而导致的奥氏体组织。另外,以12 mm/s的激光熔覆速度制备的涂层及其界面比6 mm/s情况下制备的涂层及其界面具有更高的硬度,而涂层/基体界面上的晶界与对应的晶粒相比具有更高的摩擦因数。同时,激光熔覆速度越快,界面上的晶粒尺寸越细小,界面处Ni和Fe的扩散速度越低,摩擦学性能越优异。 相似文献
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45钢表面WC-12Co金属陶瓷激光熔覆层的组织与性能研究 总被引:4,自引:3,他引:1
采用火焰喷涂技术,在45钢表面预置一层WC-12Co并进行激光熔覆实验.SEM分析试样显微组织与形貌,EDS分析界面元素分布特性,HXD-1000B维氏显微硬度仪分析显微硬度分布特征.结果表明,经激光熔覆后,火焰喷涂层所固有的片层状组织消失,形成了较为致密的熔覆层,涂层与基体间呈现冶金结合状态;熔覆层显微组织由表及里依次呈现多边形块状、枝晶状、颗粒状.熔覆层表层硬度最高,随着深度的增加,硬度逐渐下降,熔覆层与基体界面处硬度发生突变. 相似文献
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《铸造技术》2017,(10):2415-2418
采用激光熔覆的方法在20Cr Mo活塞连杆钢表面制备了Fe-20Cr、Fe-30Cr和Fe-40Cr涂层,研究了不同Cr含量的铁基熔覆层的界面形貌、物相组成、电化学性能和腐蚀磨损性能。结果表明,激光熔覆Fe-20Cr、Fe-30Cr和Fe-40Cr涂层与基体实现了较为良好的冶金结合,基体与熔覆层的界面结合处都没有发现显微孔洞、夹杂或者裂纹的存在;3种激光熔覆涂层的点腐蚀电位都更高,抗点腐蚀能力优于20Cr Mo基材;随着激光熔覆涂层中Cr元素含量的增加,涂层的抗腐蚀磨损性能有所提高,且3种激光熔覆涂层的抗腐蚀磨损性能均明显优于活塞连杆20Cr Mo基材。 相似文献
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激光熔覆原位析出增强颗粒热力学及显微组织研究 总被引:1,自引:1,他引:0
把理论与试验相结合,通过热力学理论计算,选择出合理的激光熔覆涂层体系,利用横流CO2激光器在铜合金表面激光熔覆Ni基复合材料涂层,原位自生陶瓷颗粒增强相.通过对激光熔覆涂层反应体系△GT的计算及XRD分析得知:TiB增强颗粒可以原位生成.利用OM、SEM和显微硬度计,分析测定涂层的显微组织形貌和截面显微硬度分布情况.结果表明:熔覆层与基体具有良好的结合界面,涂层内枝晶组织细小均匀.熔覆层平均显微硬度比基体显著提高,约为基体平均硬度值的3倍. 相似文献
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激光熔覆涂层能够改善金属表面性能,实现表面强化,然而常发现由于涂层韧性降低,涂层表面出现裂纹缺陷问题。概述了激光熔覆涂层由于韧性降低造成裂纹的原因,包括温度梯度差引起的内应力、激光熔覆层中的应力集中以及熔覆层中的微小气孔等。同时归纳了影响激光熔覆层韧性的因素,包括熔覆材料的选择、激光熔覆工艺参数的设定以及熔覆材料的热处理方式等。在此基础上,重点阐述了近年来改善激光熔覆涂层裂纹缺陷问题的进展,并从中寻找增强激光熔覆涂层韧性的方法,包括在熔覆粉体中加入复合陶瓷增强相和稀土元素粉末等改变熔覆粉体组成、在基体与熔覆层之间增加过渡层、改变激光熔覆功率和扫描速率以及光斑直径等工艺参数、对熔覆前基体的预热和熔覆后涂层的热处理、外加超声振动和电磁场以及超声振动与电磁场的耦合等能场辅助等。针对各种增强激光熔覆涂层韧性方法的不足,探讨今后激光熔覆涂层增韧改性方法的研究前景。 相似文献
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Guan-Jun Yang Chang-Jiu Li Cheng-Xin Li Katsuyoshi Kondoh Akira Ohmori 《Journal of Thermal Spray Technology》2013,22(1):36-47
The mechanical properties and related performance of thermally sprayed ceramic coatings are degraded by their relatively low adhesion and cohesion resulting from the limited bonding at substrate/splat interface and splat/splat interface. In this study, the influence of high strength adhesive infiltration on the microstructure and erosion performance of plasma-sprayed Al2O3 coatings was investigated to understand the improving mechanism of adhesion and cohesion through heterogeneous modification of nonbonded interfaces. Element distribution maps proved that the adhesive can be infiltrated from the coating surface to the coating/substrate interface through the inter-connected open pores including in-plane nonbonded area and microcracks in splats. Both adhesion and cohesion can be significantly improved by the heterogeneous modification of nonbonded lamellar interfaces of both splat/splat and splat/substrate through adhesive infiltration. The adhesive strength of the coating was increased from several MPa to ~50 MPa after adhesive infiltration. The erosion resistance at a large particle jet angle was improved by a factor of 3 due to the significant improvement of the lamellar cohesion, although the erosion resistance at a small particle jet angle was not significantly influenced. 相似文献
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(Ti,Al)N涂层应力沿层深分布的调整及大厚度涂层的制备 总被引:1,自引:0,他引:1
利用电弧离子镀技术在不锈钢基体上制备了(Ti,Al)N涂层,研究了N2分压改变对涂层残余应力沿层深分布及相关力学性能的影响.结果表明,低N2分压下,(Ti,Al)N涂层残余应力沿层深分布较均匀,随N2分压的增加,涂层应力沿层深呈"钟罩型"分布,且全膜厚的应力值也明显增大;通过对涂层生长结构及微观成分分析,初步探讨了应力分布机理.随N2分压的增加,涂层硬度会显著增加,而膜/基结合力则大幅下降;采用改变N2分压工艺制备(Ti,Al)N涂层,可有效调整涂层残余应力沿层深分布趋势,改善其力学性能,并可成功制备厚度在130μm以上的硬质涂层. 相似文献
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在运用有限元软件,分别对在受相同表面载荷作用下的单覆层体、三明治覆层体及梯度覆层体的滑动接触进行了弹一塑性计算。结果表明梯度硬覆层体在改善界面附近应变、应力场及裂纹应力分布场等方面比其它覆层体具有较明显的优点。三明治层能有效地减小膜层与基体间的应力值,且在界面处裂纹尖端处的应力也很小,但接近界面处的应力、应变梯度却很大。普通多层膜与单层膜相比,应力、应变分布没有很大的改进。 相似文献
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用球滚接触疲劳法评定硬质薄膜的结合强度 总被引:8,自引:0,他引:8
采用滚动接触疲劳法对气相沉积硬质薄膜的结合强度进行了研究。结果表明,反映膜基结合强度的力学参量为界面最大剪应力幅。采用数值计算的方法,可以定量得到膜基界面处的应力分布。 相似文献
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Xunzhong Guo Yannan Ma Kai Jin Hui Wang Jie Tao Minyu Fan 《Journal of Materials Engineering and Performance》2017,26(9):4235-4244
Ni/Al laminates are of great interest in many aerospace and military applications due to their excellent mechanical properties. However, their application has been limited in part due to challenges related to fabricating complex geometries. However, explosive welding is regarded as a promising technique to fabricate laminates. However, it is difficult to fabricate Ni/Al/Ni laminates with high interfacial shear strength and ductility if the stand-off distance has not been optimized during the explosion process. The goal of this study was to investigate the effect of stand-off distance on the microstructure and mechanical properties of Ni/Al/Ni laminates, and SEM and EDS were used to characterize the morphology and element distribution of the double layer interface. Tensile and tensile-shear tests were conducted to evaluate the mechanical properties of the laminates. The results indicated that with the increase in stand-off distance, three different kinds of interface were obtained (straight, wavy and continuously melted). Thickness of atomic diffusion layer increased with the increase in stand-off distance. Moreover, the Ni/Al/Ni laminates with wavy interface possessed highest value of ductility and interfacial bonding strength. 相似文献
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In clinical applications, the mechanical failure of HA-coated titanium alloy implants suffered at the interface of the HA coating and titanium alloy substrate will be a potential weakness in prosthesis. Yttria stabilized zirconia (YSZ) reinforced HA coatings have been proven to enhance the mechanical properties of the HA coating significantly and reduce the formation of calcium oxide (CaO). In this paper, HA/YSZ (30 wt.% YSZ) composite coatings were sprayed by the plasma technique. The effects of the powder processing–mechanical ball milling method and spheroidization method on the microstructure and mechanical properties of the HA/YSZ composite coatings were evaluated. The experimental results showed that the spheroidized powders melted better than the ball milled powders during plasma spraying and formed higher mechanical property coatings (1.6326±0.08 MPa m−0.5 of fracture toughness, 58.59±2.91 GPa of elastic modulus and 43.42±2.53 MPa of tensile bond strength). HA/YSZ solid solution formed during deposition on the substrate, which played a very important role in the mechanical properties of the HA/YSZ composite coatings. Tensile bond strength tests showed that the fracture mode was cohesive and that failure occurred at the interface of HA and unmelted YSZ particles. The molten state of YSZ had a great influence on the properties of the HA/YSZ composite coatings. 相似文献
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A hard ceramic coating on elastic steel substrates has been increasingly used in the tribological applications in order to reduce wear rates and friction. In case a surface pressure is applied to the coating surface of a coating–substrate system, the stress and deformation states inside the coating and at the edges of the coating–substrate interface play important role in service life of the coating. In this study, the geometrically non-linear stress analysis of a thin hard coating–elastic substrate system subjected to a surface pressure was carried out using the incremental finite element method (IFEM) based on the small strain–large displacement theory (SSLD). The pressure distribution was considered for plane-strain and axisymmetric cases. The comparison of the stress distributions of an uncoated substrate determined analytically with the results of both the SSLD analysis and the small strain–small displacement (SSSD) analysis showed a good agreement. In addition, the stress analysis of a thin coating/substrate system was carried out based on the SSLD and SSSD theories. The stress distributions along the coating surface, coating–substrate interface and across the coating and substrate were investigated in detail. Both theories showed that the normal and shear stresses became critical in the coating and on the coating–substrate interface regions corresponding to the centre and ends of the surface pressure distribution. These stresses are a probable reason of the coating–substrate detachment encountered in practice. However, the SSSD theory can not predict accurately lower stress and strain variations arising at the edges of the coating and the coating–substrate interface since the SSSD theory neglects the effects of the large displacements whereas the SSLD theory found that the normal and shear stresses and strains at these critical locations had also non-linear variations as the applied load is increased. Increasing the coating modulus resulted in higher stresses in the coating and at the edges of the coating–substrate interface. In case of a thin coating, these critical stresses occurred in the substrate whereas they spread completely inside coating regions neighboring the coating–substrate interface for relatively thicker coatings. The SSLD analysis also predicted lower and non-linear normal, shear stress and strain variations at the critical locations in the coating and on the coating–substrate interface for different modulus ratios and coating thicknesses. Since the peak stresses arising along the coating surface and the coating–substrate interface were dependent on both the coating thickness and modulus it was not possible to determine an optimum coating thickness and modulus ratio reducing all stress components causing the coating failure. However, optimum coating thickness and modulus can be searched in a large solution space using the optimization techniques. 相似文献
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Abeer Shmait Ramadan Awad Hanan T. Rahal Michele Azouri Ashraf M. Abdel-Gaber 《工业材料与腐蚀》2021,72(5):859-867
Zinc oxide (ZnO) nanoparticles (NPs) were synthesized using the coprecipitation method. The resulting NPs were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The surface morphology of the coatings has been characterized by scanning electron microscopy (SEM). SEM images show a uniform and homogeneous distribution of ZnO-NPs in polyurethane (PU) coatings while aggregates appear in epoxy coatings. Using tensile stress–strain test, the effect of the addition of ZnO-NPs on the mechanical properties of PU and epoxy coatings was examined. The addition of ZnO-NPs has enhanced the Young's modulus and the tensile strength of PU and epoxy coatings. Through the open-circuit potential and electrochemical impedance spectroscopy measurements, the anticorrosive properties of PU- or epoxy-coated mild steel panels containing ZnO-NPs have been investigated in 0.5 M NaCl solution. Nyquist impedance plots for PU and epoxy coatings in PU- or epoxy-coated mild steel panels containing ZnO-NPs were tested in the absence and presence of ZnO-NPs have different responses. It has been shown that the dispersion of ZnO-NPs significantly improves the anticorrosive performance of PU coatings. A PU coating containing 700 mg/kg ZnO-NPs is recommended to achieve better mechanical properties and corrosion resistance. 相似文献
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激光熔覆高熵合金涂层摩擦磨损行为的研究主要聚焦在涂层表面,鲜有对熔覆层/基体界面区域的摩擦学行为进行研究。为了提高AISI 1045钢的耐磨性,采用激光熔覆技术在AISI 1045钢基体表面制备宏观形貌良好、组织均匀的FeCoCrNiAl0.5Ti0.5高熵合金涂层。利用OM、XRD、SEM、EDS和摩擦磨损测试仪对激光熔覆FeCoCrNiAl0.5Ti0.5涂层的微观结构、物相组成、界面特性和摩擦磨损性能进行研究。通过对FeCoCrNiAl0.5Ti0.5涂层XRD图谱和元素分布分析发现,涂层主要由面心立方(Fe,Ni)相和体心立方相(BCC)形成的共晶组织及其中弥散分布着的Ni Al金属间化合物构成。硬度测试表明,从涂层顶部到基体,涂层、稀释区、热影响区和基体的平均显微硬度分别为518±20、561±63、473±81和217±12 HV0.2。涂层/基体界面区域生成了Cr23C6,在摩擦过程中会形成一层摩擦... 相似文献